1. Field of the Invention
The present invention is related to a driving circuit of an LCD device and related driving method, and more particularly, to a driving circuit of an LCD device and related driving method which improves cold-start.
2. Description of the Prior Art
Liquid crystals display (LCD) devices, characterized in low radiation, small size and low power consumption, have gradually replaced traditional cathode ray tube (CRT) devices and been widely used in electronic products, such as notebook computers, personal digital assistants (PDAs), flat panel TVs, or mobile phones.
FIG. 1 is a diagram of a prior art LCD device 100, and FIG. 2 is a diagram of a prior art LCD device 200. The LCD devices 100 and 200 each include a liquid crystal display panel 110, a timing controller 120, a source driver 130, a gate driver 140, a plurality of data lines DL1-DLm, a plurality of gate lines GL1-GLn, and a pixel matrix. The pixel matrix includes a plurality of pixel units PX each having a thin film transistor switch TFT, a liquid crystal capacitor CLC and a storage capacitor CST, and respectively coupled to a corresponding data line, a corresponding gate line and a common voltage VCOM. The timing controller 130 may generate control signals and clock signals for operating the source driver 130 and the gate driver 140. Therefore, the source driver 110 may generate data driving signals SD1-SDm corresponding to display images, and the gate driver 140 may generate the gate driving signals SG1-SGn for turning on the TFT switches.
In the LCD driver 100 illustrated in FIG. 1, the gate driver 140 is an external driving circuit which outputs the gate driving signals SG1-SGn using a plurality of gate driver integrated circuits (ICs) 142. In the LCD driver 200 illustrated in FIG. 2, the gate driver 140 and the pixel units PX are both fabricated on the LCD panel 110 using gate on array (GOA) technique. The gate driver 140 of the LCD driver 200 may thus output the gate driving signals SG1-SGn using a plurality of shift register units SR1-SRn, thereby reducing the number of chips and signal lines.
Traditional gate ICs and GOA gate drivers both require shift register units and level shifters for signal enhancement. In traditional gate ICs, the shift register units and the level shifters are integrated into a single chip in a CMOS process. In GOA gate drivers, the shift register units are fabricated in a TFT process and the level shifters are integrated into a pulse width modulation integrated circuit (PWM IC). Since the conducting current ION of a TFT switch is proportional to its gate voltage VGH and inversely proportional to its operational temperature, the turn-on speed of the TFT switch decreases as the environmental temperature drops. The difficulty of turning on the TFT switch in low-temperature environment is known as “cold-start”. In the prior art, the gate voltage VGH of the TFT switch is increased for increasing the conducting current ION in low-temperature environment, which may cause extra power consumption.